Multiple crystal growing head



Aug. 11, 1964 c. M. TARTER 3,144,308

MULTIPLE CRYSTAL GROWING HEAD Filed July 3, 1961 3 Sheets-Sheet l Fig. I.

INVENTOR. Carl M. Turier 1-964 c. M. TARTER 3,144,308

MULTIPLE CRYSTAL GROWING HEAD Filed July 3, 1961 3 Sheets-Sheet 2 Fig.2.

Fig.6. Fig. 7.

INVENTOR. Carl M.. Torfer 1964 c. M. TARTER 3,144,308

MULTIPLE CRYSTAL GROWING HEAD Filed July 5, 1961 3 Sheets-Sheet 5 n7" I l I08 97 37 I07 A I I r 66 63 57 83 INVENTOR. Curl M.Turter y-IG 2 United States Patent ()fi ice 3,144,3fi3 Patented Aug. 11, 1964 3,144,308 MULTEILE CRYSTAL GROWING HEAD Carl M. Tartar, 15625 Redwood Highway N., Healdsburg, Calif. Filed July 3, 1961, Ser. No. 123,354 8 Claims. (Cl. 23-273) This invention relates to a new and useful improvement in multiple crystal growing head. More particularly the present invention relates to a modification of existing crystal growing equipment of the type for silicon crystals and the like. In such conventional machines there is provided a crucible which is heated to a temperature sufficient to melt the silicon or other material being crystallized and which is sealed from the atmosphere and blanketed with an inert gas such as helium. A seed rod is inserted in the crucible and rotated and causes the formation of a crystal at the base of the rod. As the crystal grows the rod is raised and thereby the crystal is elongated.

The present invention comprises an improvement on such equipment which makes it possible to grow a plurality of crystals at one time from a single crucible.

A particular feature and advantage of the present invention is the fact that the temperature at the base of each of the seed rods may be adjusted individually. Such adjustment is accomplished by moving the rod in a radial direction with respect to the crucible, it being understood that the crucible is hottest at its exterior where the heating coils are located.

A further feature and advantage of the present invention is the fact that means is provided to seal the head to the crucible, which seal is maintained regardless of the position of adjustment of each of the rods and which further permits the radial adjustment of the rods through a wide range.

Another advantage of the invention is the fact that each rod may be adjusted to a position very close to the center of the crucible, thus further facilitating a wide variation in temperature of the various seed rods.

Still another feature of the invention is the fact that each of the rods is maintained in vertical alignment independently of the others and is supported top and bottom, the top and bottom supports moving inwardly and outwardly equidistantly for each individual rod.

Still a further feature of the invention is the provision of means for individually adjusting the speed of each rod if required.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a side elevation of a portion of a crystal growing machine with the present invention incorporated therein.

FIGS. 2 and 3 are transverse horizontal sectional views taken substantially along the lines 22 and 3-3, respectively, of FIG. 1.

FIGS. 2a and 3a are fragmentary sectional views taken along corresponding lines in FIGS. 2 and 3, respectively.

FIG. 4 is a fragmentary enlarged vertical sectional view taken substantiflly along the line 44 of FIG. 2.

FIG. 5 is a fragmentary enlarged sectional view through the gas slide mechanism showing such mechanism in a different position of adjustment from that shown in FIG. 4.

FIGS. 6 and 7 are plan views of the top and bottom gas slides respectively.

Crystal growing equipment is well understood in this art and only portions of a machine for such purpose are illustrated herein. A base plate 11 is provided horizontally disposed and supported by legs 12. Mounted on base plate 11 is a crucible 13 which is in turn rotated by means of crucible rotating shaft 14 vertically disposed and driven by means forming no part of the present invention and not herein illustrated in detail. Surrounding crucible 13 is a casing 16 and around casing 16 are heating elements 17 which heat crucible 13 to a temperature sufficient to melt the material contained therein. Such material may be silicon in a preferred embodiment of the invention.

Spaced at a variable distance above base plate 11 is a superstructure 21 having a horizontal web 22 provided with a bearing 23 in which is vertically rotatable a rod driveshaft 24. Driveshaft 24 is driven by electric motor 26 through pulleys 2723 and interconnecting belt 29. To raise and lower superstructure 21, there may be provided a plurality of vertical screws 31 mounted in base plate 11 which are driven in synchronism by means not herein illustrated, screws 31 being in threaded engagement with nuts 32 on superstructure 21 so that as screws 31 turn the superstructure is raised relative to crucible 13. The rate of elevation of superstructure 21 is related to the rate of growth of the crystals in the crucible.

The present invention is concerned primarily with the crystal growing head 36 located between superstructure 21 and casing 1-5. Head 3%? comprises a number of eleients which are supported primarily by means of top and bottom plates 37, 33, respectively. Top plate 37 depends from web 22, there being a bracket having center portion 39 fastened to web 22 and vertical legs 41, lower ends of bracket legs 41 having feet 42 connected to top plate 37. Bottom plate 38 rests upon casing 16 and is sealed thereagainst by means of gasket 43 inserted in a groove 44 in the bottom of plate 38 and sealing against the upper edge of casing 16. Side lugs 46 are attached to the perimeter of plate 38 and formed with vertical holes to receive rods 47 on base plate 11. A gas such as helium is fed into casing 16 through fitting 48 in plate 38 and is connected to a suitable source of gas. The purpose of the gas is to blanket crucible 13 and prevent oxidation of the contents and is under sufficient pressure to prevent entry of atmosphere into casing 16. Further, it is desirable that bottom plate 38 be cooled, and for such purpose passageways 51 for cooling water are provided in the top surface of plate 38. An annular cover ring 52 is positioned over the cooling water passageways 51 to form an enclosure, and suitable water inlet and outlet connections 53, 54 provided to maintain circulation of water through the cooling passageways. Gaskets 56 in circular grooves 57 seal ring 52 to plate 38.

In accordance with the present invention there are provided a plurality of seed rods 61 here shown as three in number and A1 inch in diameter. Such seed rods 61 extend from a position slightly above top plate 37 through bottom plate 38 and into casing 16 and into crucible 13. The lower tips of rods 61 comprise the seed around which the crystals of silicon or the like grow. As the crystals grow rods 61 are raised by upward movement of superstructure 21. The present invention provides means for rotating rods 61 individually from the driveshaft 24 and at the same time moving rods 61 radially each independently of the other.

For purpose of permitting radial movement of rods 61 relative to bottom plate 33, there are provided in bottom plate 38 three radially disposed slots 62. The slots 62 are preferably of an effective length of about /2 inch and permit each rod 61 to move from adjacent the central axis of crucible 13 outwardly a distance of /2 inch. Such radial movement permits considerable adjustment in the temperature at the base of the rod.

To prevent escape of gas through the portion of slots 62 not occupied by rods 61, the top surface of bottom plate 38 is formed with radially extending grooves 63 in alignment with slots 62, and within grooves 63 are top and bottom horizontally slidable gas slides 64, 66 formed of a material such as 50% glass Teflon. Top slide 64 is formed with a hole 67 which is of the width of seed rod 61 and is slightly elongated to an elfective length about .100 inch greater than the diameter of said rod 61. Bottom slide 66 is longer than top slide 64 and is formed with an elongated slot 68 having an elfective length about .312 inch greater than the diameter of seed rod 61. The lengths of the slides 64, 66 and of the slots 67, 68 therein are such that when rod 61 is moved radially by means hereinafter explained, the slides at all times conceal slot 62 except for the passageway of rod 61 therethrough. To facilitate sliding movement of slides 64, 66 there is a vertical pin 69 located in center of plate 38 where the three grooves 63 converge. When rod 61 is at the extreme outer position of its movement as shown in FIG. 5, the outer ends of slides 64, 66 abut the outer end 71 of groove 63. As rod 61 is moved inwardly it pushes top slide 64 inwardly (because of the restricted length of slot 67), the progression of such movement being shown by contrast of FIG. with FIG. 4. Further inward movement beyond that shown in FIG. 4 causes rod 61 to engage the inner end of slot 68 of lower slide 66 and to move slide 66 radially inwardly until it contacts pin 69 which stops the movement. Thus, regardless of the radial position of rod 61, slot 62 is closed off by slides 64, 66. Downward pressure of slides 64, 66 is maintained by means of adjustment block 72, or guide there being one such block 72 for each rod 61. Adjustment block is held to permit radial movement but prevent vertical movement by gibs 73 fastened to plate 38 and having projections 74 fitting into horizontal grooves 76 in block 72. Adjustment block 72 has a vertical bore 77 for seed rod 61 provided with seal 78 surrounding rod 61 and held in place with proper adjustment of pressure by means of cap 79. A threaded horizontally radially outwardly facing hole 81 receives the threaded inner end of adjustment screw 82. Adjustment screw 82 extends radially outwardly and is supported at the outer edge of plate 38 by means of bearing block 83. Adjustment knob 84 on the outer end of screw 82 permits manual turning of screw 82 and such movement is transformed into radial movement of block 72 and of the rod 61 supported therein. Each rod 61 is individually adjustable by turning its knob 84.

As previously stated, a feature of the present invention is the provision of means whereby the upper end of each rod 61 is moved in a radial direction a distance equal to the movement of the lower end of the rod. For such purpose for each seed rod 61 there is mounted on screw 82 a bevel gear 86 which meshes with bevel gear 87 on the lower end of a vertically disposed splined rod 88 which passes through upper plate 37. Upper plate 37 carries a bevel gear 89 rotatably mounted thereon and turning with splined rod 88 but vertically slidable along rod 88, and gear 89 meshes with gear 91 journalled in upper bearing block 92 on plate 37 and carrying upper lead screw 93. Upper lead screw 93 is threaded into a bore 94 in upper block 96 or guide which moves in a radial direction in radial slot 97 in plate 37. Gibs 98 fastened to plate 37 have projections 99 fitting into horizontal grooves 101 in block 96 and guiding block 96 for horizontal radial movement only. Bearings 102, 103 are mounted at the top and bottom of block 96 to receive seed rod 61. The upper bearing 102 carries a stop 104 which is attached to rod 61 by means of set screw 106 and lower bearing 103 carries a similar stop 107 likewise attached to rod 61 by set screw 108. This insures that rod 61 moves vertically as upper plate 37 moves. Upper stop 104 also carries a pinion 109 which meshes with pinion 111 on spindle 112 rotatably mounted by means of bearings 113 in block 96. The upper end of spindle 112 has a groove 114 which functions as a pulley and is connected to groove 116 in lower end of drive rod 24 by means of belt 117. Belt 117 is elastic so that as block 96 moves radially the drive between drive rod 24 and spindle 112 is maintained. It will be noted that the elevation of the grooves 114 in the three spindles 112 for the three seed rods 61 are different but that in all other respects the means for moving the seed rods radially is identical.

Operation The essential operation of the apparatus heretofore described is in several respects the same as in conventional crystal growing apparatus. Thus the crucible 13 is provided with silicon or similar material to form the crystal. Heat is applied to the heating coil 17 which raises the material to its melting point, it being observed that the material is hottest at its perimeter where it is adjacent the heating coils and that the temperature decreases as the distance from the perimeter increases. Crucible 13 is rotated by shaft 14 by means well understood in this art and not illustrated herein. At the outset, seed rods 61 are installed in each of slots 97, the upper end of the rod being retained to move with upper plate 37 by means of stops 104 and 107 in engagement therewith. The seed rods 61 extend through packing 78 and through the apertures 67, 68 in upper and lower slides 64, 66 thence through the slot 62 in lower plate 38 and through casing 16 into crucible 13. Each rod 61 is caused to rotate by reason of rotation of drive rod 24, belt 117, spindle 112, and gears 111-109, the latter of which is rotatable with stop 104 and rod 61. As the crystals form on the bottom of seed rod 61, the rod is gradually raised by turning screws 31 which in turn raises superstructure 21 and upper plate 37. Upper plate 37 slides along the splined drive rod 88.

It is desirable that the temperature of the crystal formed at the bottom of each seed rod be maintained at the optimum and this requires inward and outward movement of the seed rod in a radial direction. This is accomplished by turning adjustment knob 84 on lower threaded rod 82. By reason of the gear train 86, 87 and rotation of the splined rod 88 and gear train 89-91 an equal turning movement is imparted to upper threaded rod 93. This results in lower block 72 and upper block 96 moving radially an identical distance and hence seed rod 61 is at all times vertical regardless of its position of adjustment.

A gas such as helium is maintained inside casing 16 to prevent oxidation. Such gas is admitted to the casing through port 48. Slides 64-66 prevent escape of the gas. Thus when the seed rod 61 is at its outer limit, lower slide 66 is retracted until its outer end abuts the outer end 71 of groove 63 in which the slide is mounted and thereafter outward movement of the lower slide ceases. In such position, as shown in FIG. 4, the inner end of lower slide 66 overlaps the inner end of slot 62 and hence the seal is maintained. Further inward movement of seed rod 61 is permitted by reason of sliding of the upper slide 64 over lower slide 66 and such movement is continued until the position of FIG. 5 is reached, which position is the outer limit of movement of the seed rod and brings the outer end of upper slide 64 into contact with the end 71 of groove 63. The inward movement of the seed rod 61 from the extreme position of FIG. 5 first moves the upper and lower slides 64, 66 to the position shown in FIG. 4. Further inward movement results in inward movement of the lower slide 66 until its inner end abuts central pin 69, at which time the seed rod has reached the limit of its inward movement.

It will thus be seen that the three seed rods 61 may be moved in a radial direction, each independently of the other by adjustment of its respective adjustment knob 84 even when the rods are rotating. The limit of the move ment is the length of slot 62. Regardless of the position of adjustment of the seed rod, a seal is maintained by slides 64, 66. As the crystal is formed and as the upper plate is raised 37, the adjustment is maintained by reason of gear 89 on upper plate 37 sliding along splined rod 88. Regardless of the radial position of seed rod 61, the driving relationship between drive shaft 24 and the seed rod is maintained because of the fact that belt 117 stretches to permit the radial movement.

Although the foregoing invention has been described in some detail, by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention and scope of the appended claims.

What is claimed is:

l. A crystal growing head comprising a lower plate formed with at least one radial first slot, a top plate above and vertically movable relative to said lower plate and formed with a second slot vertically aligned with said first slot, 2. seed rod extending through said slots and below said first plate, a first guide apertured for said seed rod, first means mounting said first guide for movement on said lower plate parallel to said first slot, a second guide apertured for said seed rod and mounting said seed rod for vertical movement with said top plate and rotative movement, second means mounting said second guide for movement on said top plate parallel to said second slot, adjustable third means for adjusting the radial position of said first guide, fourth means interconnecting said first and second means for equal radial movements of said first and second guides, and sealing means interposed between said bottom plate and said first guide sealing against escape of gas through said first slot around said seed rod.

2. A head according to claim 1 in which said fourth means is vertically extensible.

3. A head according to claim 1 in which said fourth means comprises a vertical rod interconnecting said top and bottom plates and gear trains for transmitting motion from said third means to said rod and from said rod to said second guide.

4. A head according to claim 1 in which said sealing means comprises a bottom slide and a top slide parallel to said bottom slide, said slides being interposed between said bottom plate and said first guide over said first slot, means confining said slides to radial movement and inner and outer abutments limiting radial movement of said slides to the length of said first slot, each said slide being formed with an aperture to receive said seed rod, one of said apertures being elongated in a radial direction.

5. A crystal growing head comprising a lower plate formed with a plurality of radial first slots, a top plate above said lower plate formed with a corresponding plurality of second slots vertically aligned with said first slots, means for raising and lowering said top plate relative to said lower plate, a seed rod for each said first slot extending through a first and a second slot and movable radially therein, and for each said rod a first guide vertically apertured to receive said seed rod, first means mounting said first guide for movement on said lower plate parallel to said first slot, a second guide rotatably mounting said seed rod for movement therewith, second means mounting said second guide for movement on said top plate parallel to said first slot, third means manually adjustable for moving said first guide radially on said lower plate along said first slot, fourth means for moving said second guide radially on said top plate, fifth means for moving said third and fourth means equal radial distances, said fifth means being vertically extensible to permit relative vertical movement of said top and bottom plates, and sealing means interposed between said bottom plate and said first guide sealing oil said first slot around the perimeter of said seed rod to prevent escape of gas through said seed rod.

6. A head according to claim 5 in which said sealing means comprises a bottom slide and a top slide parallel to said bottom slide, said slides being interposed between said bottom plate and said first guide over said first slot, means confining said slides to radial movement and inner and outer abutmen'ts limiting radial movement of said slides to the length of said first slot, each said slide being formed with an aperture to receive said seed rod, one of said apertures being elongated in a radial direction.

7. A crystal growing head comprising a lower plate formed with a plurality of first slots each radially disposed, a top plate above and vertically movable relative to said lower plate and formed with a plurality of second slots vertically aligned with said first slots, a plurality of seed rods each extending through one of said first and one of said second slots, means mounting said rods for moving each said seed rod individually radially within said slots, and sealing means for each said seed rod sealing around said seed rod over said first slot and against said lower plate, said sealing means being operable in any position of radial movement of said seed rod.

8. A head according to claim 7 in which said sealing means comprises a guide around said seed rod mounted for movement over said lower plate, a top and bottom slide between said guide and said lower plate over said first slot, means confining said slides to radial movement and abutment means limiting radial movement of said slides, each said slide being formed with an aperture to receive said seed rod, one of said apertures being elongated in a radial direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,935,385 Cornelison g May 3, 1960 

1. A CRYSTAL GROWING HEAD COMPRISING A LOWER PLATE FORMED WITH AT LEAST ONE RADIAL FIRST SLOT, A TOP PLATE ABOVE AND VERTICALLY MOVABLE RELATIVE TO SAID LOWER PLATE AND FORMED WITH A SECOND SLOT VERTICALLY ALIGNED WITH SAID FIRST SLOT, A SEED ROD EXTENDING THROUGH SAID SLOTS AND BELOW SAID FIRST PLATE, A FIRST GUIDE APERTURNED FOR SAID SEED ROD, FIRST MEANS MOUNTING SAID FIRST GUIDE FOR MOVEMENT ON SAID LOWER PLATE PARALLEL TO SAID FIRST SLOT, A SECOND GUIDE APERTURED FOR SAID SEED ROD AND MOUNTING SAID SEED ROD FOR VERTICAL MOVEMENT WITH SAID TOP PLATE AND ROTATIVE 